Self-developing photographic film unit and process having secured face-to-face surface

ABSTRACT

A photographic film unit comprising all of the materials, including a liquid processing agent, required to produce a photographic print and a method of rapidly spreading a viscous liquid processing agent in a continuous uniform layer between a pair of superposed sheets without entraining air in the liquid. A film unit is disclosed comprising a photosensitive sheet and a transparent sheet secured in face-to-face relation at the edges of the sheets and a collapsible container of a viscous processing liquid secured at one edge of the sheets so as to discharge its fluid contents between the sheets when compressive pressure is applied to the container. A method is disclosed in which the sheets are held in face-to-face contact to exclude air from between the sheets during spreading of the processing liquid therebetween facilitate spreading and to preclude entrainment of air in the liquid.

United States Patent [72] Inventor Edwin H. Land Cambridge, Mass. [21 1 Appl. No. 622,287 [22] Filed Mar. 10, 1967 [45] Patented Oct. 26, 1971 [73] Assignee Polaroid Corporation Cambridge, Mass.

[54] SELF-DEVELOPING PHOTOGRAPHIC FILM UNIT AND PROCESS HAVING SECURED FACE-TO- 2,600,064 6/1952 McCune 96/76 Primary ExaminerNorman G. Torchin Assistant Examiner.lohn L. Goodrow Attorneys-Brown and Mikulka and Robert E. Corb ABSTRACT: A photographic film unit comprising all of the materials, including a liquid processing agent, required to produce a photographic print and a method of rapidly spreading a viscous liquid processing agent in a continuous uniform layer between a pair of superposed sheets without entraining air in the liquid. A film unit is disclosed comprising a photosensitive sheet and a transparent sheet secured in faceto-face relation at the edges of the sheets and a collapsible container of a viscous processing liquid secured at one edge of the sheets so as to discharge its fluid contents between the sheets when compressive pressure is applied to the container. A method is disclosed in which the sheets are held in face-toface contact to exclude air from between the sheets during spreading of the processing liquid therebetween facilitate spreading and to preclude entrainment of air in the liquid.

PATENTEDuc-I 26 I97! 3,615,539 SHEET 2 BF 2 FIG.4

ATTORN EYS SELF-DEVELOPING PHOTOGRAPHIC FILM UNIT AND PROCESS HAVING SECURED FACE-TO-FACE SURFACE The film unit of the invention is adapted to be employed in and the process of the invention is adapted to be performed by a self-developing camera of the type shown and described in the copending U.S. Pat. application of Robert L. Norton Ser. No. 604,304, filed Dec. 23,1966, now U.S. Pat. No. 3,426,665, granted Feb. 1 l, 1969, in which a completely, selfcontained film unit is exposed and then processed by moving it relatively rapidly between a pair of pressure-applying members. The component of the film unit are assembled together to form an integral structure and the integrity of this structure is maintained during exposure and processing, thereby making it unnecessary to store, handle and/or move separately, individual elements of the film unit and minimizing the complexity of the structure required to contain and manipulate the film unit to effect exposure and processing thereof. Further reduction in the complexity of the exposure and processing mechanisms of the camera can be realized by combining the functions of components of the apparatus, specifically, by exposing the film unit during movement thereof by the processing means which may comprise a pair of pressure rollers. This type of exposure and processing system necessitates movement of the film unit during processing a speed that is relatively rapid, e.g., of the order of 9 inches per second, is accurately predetermined, is governed within relatively narrow limits and, in the case of a small, compact camera, must be achieved with a motor having a minimum of power. Exposure and processing of a film unit in a camera such as described presents a number of unique problems affecting the design of the film unit structure and the manner in which the film unit is stored, handled and manipulated.

The solutions to these problems and the objects of the invention are to provide a film unit structure that is attractive, includes a minimum of simple and and easily assembled components, is of a minimum size in relation to image size and generally includes substantially no excess materials, includes the processing liquid and means for promoting and facilitating spreading of the liquid in a layer of predetermined depth and extent, is inexpensive and functions reliably and well; and to provide a method of processing a film unit of this type enabling the rapid and accurate spreading of a predetermined quantity of a viscous processing liquid in a layer of uniform depth completely over an area between two sheets without entraining air in the liquid while generally avoiding discontinuities in the liquid and resulting in an attractive, positive photographic print.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The film unit of the invention generally comprises two separate, flexible sheetlike elements including a first or imagerecording sheet including a layer containing a photosensitive image-recording material and a second or image-receptive sheet for aiding in the distribution of a viscous liquid processing agent as a layer in contact with an exposed area of the photosensitive material and for acting as a support for a transfer image formed by diffusion of image-forming substances from the photosensitive material-containing layer through the layer of processing liquid to the second sheet. At least one of the sheets, preferably the second sheet, is transparent to provide for exposure of the photosensitive material while the sheets are in superposition and viewing of the image formed against the inner surface of the second sheet. This construction enables the two sheets to be secured to one another at their margins to form an integral unit, the integrity of which is established prior to loading into a camera, is maintained throughout exposure and processing and can be maintained subsequent to processing. The processing liquid includes, in addition to the reagents required to produce a diffusion transfer image, a thickening or film-forming agent provided to aid in the formation of a layer of film of the liquid between sheets and an opacifying agent for masking a visible (negative) image formed in the photosensitive layer and providing a background for the diffusion transfer (positive) image formed against the inner surface of the transparent second sheet.

Film units of this general type are described, for example, in U.S. Pats. of Edwin H. Land, No. 2,873,658, granted Feb. 17, 1959, and No. 3,053,659, granted Sept. 11, 1962. These patents show structures similar to the film unit of the invention insofar as they include image-recording and image-receptive elements and containers of viscous processing liquid located externally of the elements. The film unit of the present invention is distinguished by a novel combination of features that fulfill the objectives of the invention particularly with regard to the achievement of an integral two-sheet film unit and container that is easy to store and handle before, during and after exposure and processing, the rapid spreading of the processing liquid without entraining air to produce a uniform layer of accurately predetermined thickness and the production of an attractive finished photographic print comprising a film unit, the integrity of which is maintained throughout and following exposure and processing.

The invention accordingly comprises the apparatus possessing the construction, combination of elements and arrangement of parts which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings wherein:

FIG. 1 is a perspective view, partially in section, of a photo graphic film unit embodying the invention;

FIGS. 2 and 3 are longitudinal, sectional views showing the film unit of FIG. 1 and steps in the process employing the film unit;

FIG. 4 is a transverse sectional view of the film unit illustrating a step in the process, the section being taken substantially along the line 4-4 of FIG. 3;

FIG. 5 is a view of the film unit similar to F IG. 4illustrating the completed photographic print; and

FIG. 6 is a longitudinal, sectional view of another embodiment of the film unit of the invention.

The film unit and method of the invention are adapted to the performance of a number of different image-forming processes and particularly to the production of a positive photographic print preferably in full color produced by a diffusion-transfer process in which a photographic image-recording medium including a photosensitive material such as silver halide is exposed to form an image (latent) therein and is treated by wetting with a liquid processing agent to develop the image in the image-recording medium, form and imagewise distribution of transferable image-forming substances and transfer the image-fonning substances by diffusion to an image-receptive stratum in which they are immobilized to form a visible positive image. The film unit may comprise materials for producing a black-and-white print according to a process such as disclosed in the U.S. Pats. of Edwin H. Land, No. 2,543,181, granted Feb. 27, 1951, and No. 2,662,822, granted Dec. 15, 1953. In this embodiment, the film unit may comprise an image-recording medium including, as the photosensitive material, a silver halide emulsion; a liquid processing agent including a silver halide developer and a silver complexing agent; and the material required to provide a silver precipitating environment in an image-receptive stratum of the film unit during processing. The processing liquid is distributed in contact with the layer containing the exposed image-recording medium for permeation therein to develop the latent image and form a soluble silver complex from unexposed silver halide which is transferred by diffusion to an image-receiving stratum where it is reduced to silver in the presence of a silver precipitant to form a visible positive image. The silver precipitating environment may by provided initially as a layer or stratum on one of a pair of superposed elements comprising the film unit, preferably and element different from the one including the image-recording medium,

and/or in the liquid composition distributed in a layer between the elements.

A preferred embodiment of the film unit of the invention includes all of the materials and reagents required to produce a full color photographic print by a process such as disclosed in U.S. Pat. No. 2,983,606, issued May 9, 1961 in the name of Howard G. Rogers. This patent discloses a photosensitive element including a silver halide emulsion and a dye developer, that is, a dye which is a silver halide developing agent; a second or image-receiving element including an image-receiving layer of a dyeable material; and a processing liquid in which the dye developer is soluble. The photosensitive and image-receiving elements are superposed with the emulsion and image-receiving layers in face-to-face relation and the processing liquid is distributed in a uniform layer between and in contact therewith for permeation into the photosensitive layer where it initiates development of exposed silver halide. The dye developer is immobilized or precipitated in exposed areas as a consequence of development while in unexposed areas and partially exposed areas of the emulsion, the dye developer remains unreacted and diffusible thereby providing an imagewise distribution of unoxidized dye developer which is transferred, at least in part, by diffusion to the image-receiving layer without altering the imagewise distribution of the dye developer, to form a reversed or positive color image of the developed latent image in the emulsion. Multicolor transfer images are obtained utilizing dye developers, for example, by employing an integral multilayer photosensitive element such as illustrated in FIG. 9 of the US. Pat. No. 2,983,606, including at least two selectively sensitized overlying photosensitive strata on a single support. A typical photosensitive element of this type comprises a support carrying a red-sensitive silver halide emulsion stratum, a green-sensitive silver halide emulsion stratum and a blue-sensitive silver halide emulsion stratum, the emulsions having associated therewith, respectively, for example, a cyan dye developer, a magenta dye developer and a yellow dye developer. Each set of silver halide emulsion and associated dye developer strata may be separated from other sets by suitable interlayers formed, for example, of gelatin or polyvinyl alcohol. In the example given, the dye developers are preferably selected for their ability to provide colors useful in producing a full color image by a subtractive process and may be incorporated in the respective silver halide emulsion with which they are associated or in a separate layer behind their respective silver halide emulsion. In certain instances, a yellow filter is incorporated located in front of the green sensitive emulsion and comprising a yellow dye developer or a separate layer of a yellow filter material.

Reference is now made to FIGS. 1 through 5 of the drawings wherein there is illustrated a photographic film unit 10 embodying the invention, the thickness of the materials being exaggerated for purposes of clarity of illustration. Film unit 10 comprises a photosensitive or image-recording sheet 12, a second or image-receiving sheet 14 and a rupturable container 16 holding a quantity of processing liquid 18. Sheets 12 and M are preferably rectangular and coextensive with one another and are arranged in superposed face-to-face contact with at least one edge of each sheet aligned with an edge of the other. The two sheets are retained in superposed relation by a binding element 20 in the form of a rectangular sheet larger than either of the photosensitive or image-receiving sheets and secured to the two sheets at the margins thereof. Binding element 20 is in the general form of a frame having a large rectangular opening 22 defining the extent of the image produced in the film unit, surrounded by lateral edge portions 24 and end portions 26 and 28. Sheet 12 includes lateral marginal portions 30 and an end marginal portion 34 and sheet 14 includes lateral marginal portions 32 and an end marginal portion 36 with the lateral and end marginal portions of the two sheets being located in face-to-face contact, preferably with the edges thereof in alignment. The lateral edge portions 24 and end portion 26 of binding element 20 are secured around and to, respectively, lateral marginal portions 30 and 32 of sheets 12 and 14 and end marginal portions 34 and 36 of the sheets effectively binding the two sheets to one another along three sides thereof. In a preferred form of film unit adapted to produce a reflection print surrounded by a white border and viewed against a white background, at least binding element 20 is formed of an opaque, white materialand container 16 may also include a white outer coating to provide a more aesthetically pleasing product.

Container 16 is of the type shown in US. Pat. No. 2,543,181, formed by folding a rectangular blank of a fluid im pervious sheet material medially and sealing the marginal sections of the blank to one another to form a cavity for containing processing liquid 18. The seal between longitudinal marginal sections 38 of the container is weaker than the end seals so that upon the application of a predetermined compressive force to the walls of the container in the region of the liquidfilled cavity, there will be generated within the liquid hydraulic pressure sufficient to separate longitudinal marginal sections 38 throughout the major portion of their length to form a discharge mouth at least equal in length to the length of the cavity and the width of opening 22 through which processing liquid 18 is discharged. Container 16 is attached to the sheets at the edges thereof opposite end portions 34 and 36, preferably with the longitudinal edge of the container butted against the edges of the sheets and with the discharge passage of the container aligned with the facing surfaces of the sheets. Sheets 12 and 14 include, respectively, end marginal portions 40 and 42 and the means for coupling the container to the sheets include end portion 28 of binding element 20 secured to end marginal portion 42 of sheet 14 and longitudinal marginal section 38 of the container so as to bridge the container and sheet 14; and a strip 44 secured to end marginal portion 40 of sheet 12 and the other longitudinal marginal section 38 of the container to bridge the gap between the container and sheet 12 The binding element and strip 44 cooperate to provide a liquidtight seal between the marginal sections of the container defining the discharge mouth thereof and sheets 12 and 14; and form a conduit for conducting the liquid from the container between the sheets at end marginal portions 40 and 42 thereof.

The most useful and advantageous film unit insofar as packing, storing, handling, exposure and processing are concerned, is one characterized by an integral, unitary structure constructed so that its integrity may be maintained during and after exposure and processing; and a structure that is sturdy, has some flexibility and can be handled and manipulated by mechanical means without damage to producing a useful and attractive photographic print. A useful and attractive photographic print can be described as being substantially flat or planar and without a tendency to curl as the result of temperature and humidity changes; as being relatively rigid and inflexible as opposed to being limp or easily bent; as having a uniform white border surrounding a well-defined rectangular image that extends to the border; and a protective coating or covering for the image permitting the print to be handled and stored without the necessity for taking special precautions to avoid damage and deterioration. The structure and composition of components of the film unit of the invention combined to provide a film unit meeting these criteria, and together with the steps involved in the process of the invention, are specially adapted to provide a useful and attractive photographic print, preferably in full color, having the foregoing characteristics.

In order to provide a rigid durable structure having an integrity which is maintained from the time of assembly (during manufacture) to the finished print and providing a protective environment for the photosensitive medium as well as the final image, while permitting exposure of the photosensitive medium and viewing of the final image, at least one of the sheets of the film unit is formed of a transparent material. In the em bodiment shown, the second or image-receiving sheet is transparent and the photosensitive medium is exposed and the final image is viewed through the image-receiving sheet which functions to protect both the image-recording medium and final image. In other embodiments of the film unit the photosensitive sheet may be transparent depending upon the manner in which the image-recording medium is exposed and the final image is formed and viewed. The transparent imagereceiving sheet may be formed of a conventional film base material such as cellulose triacetate coated on its inner surface with one or more layers providing an appropriate environment for the formation of a diffusion transfer image. In a film unit designed to produce a color image in terms of a dye developer, the image-receiving sheet may be prepared as disclosed in the following example, by coating a transparent cellulose triacetate film base in succession with the following layers:

1. the partial butyl ester of polyethylene/maleic anhydride copolymer prepared by refluxing, for 14 hours, 300 grams of high-viscosity poly-(ethylene/maleic anhydride), 140 grams of n-butyl alcohol and 1 cc. of 85 percent phosphoric acid to provide a polymeric acid layer approximately 0.75 mils. thick;

2. a solution of hydroxypropyl cellulose in water to provide a polymeric spacer layer approximately 0.075 mils. thick; and

. a 2:1 mixture, by weight, of polyvinyl alcohol and poly- 4- vinylpyridine, at a coverage of approximately 600 mgs./ft. to provide a polymeric image-receiving layer approximately 0.40 mils. thick.

in a preferred embodiment of the film unit useful in color photography and incorporating an image-receiving sheet prepared as described above, the image-recording sheet is preferably opaque to actinic light and is prepared by coating a succession of layers containing dye developers and specially sensitized gelatino-silver iodobromide emulsions such as disclosed in the aforementioned Rogers patent on a gelatin subbed opaque cellulose triacetate film base.

The image-recording and image-receiving elements may incorporate other strata and coatings commonly employed in photographic products of this type such as optical coatings for preventing halation and reflection and otherwise improve the optical properties of the sheet material and to facilitate and improve exposure and viewing of the final image. For further details and examples of the composition and structure of image-recording and image-receiving sheets suitable for incorporation in the film unit of the invention, reference may be had to the copending U.S. Pat. application of Edwin H. Land, entitled PHOTOGRAPHIC PRODUCTS AND PROCESSES, filed on an even date herewith as a continuation-in-part of U.S. Pat. application Ser. No. 234,864, filed Nov. 1, 1962, now U.S. Pat. No. 3,362,819 granted Jan.9, 1968.

The embodiment of the film unit illustrated and described herein is adapted to be exposed and processed to produce a multicolor dye transfer image in a dyeable polymeric layer located between a transparent film on which the dyeable polymeric layer is supported and an opaque layer located between the image and the photosensitive medium. This opaque layer comprises the liquid contents 18 of container 16 provided in sufficient quantity to form a layer of predetermined thickness, e.g., of the order of 0.004 inch, when distributed uniformly between the sheets over an area at least coextensive with opening 22 in binding element 20. The quantity of liquid 18 supplied in the container is preferably just sufficient to form a layer of the desired thickness and extent thereby making it unnecessary to provide means for collecting and retaining excess processing liquid and also providing for minimizing the size, quantity and complexity of the container, its contents and the other components of the film unit. The processing liquid contained in container 16 comprises an aqueous alkaline solution having pH at which the dye developers are soluble and diffusible and contains an opacifying agent in a quantity sufficient to mask the dye developers retained in the image-recording layer (laminate) subsequent to processing; and a film-forming viscosity increasing agent or agents to facilitate rupture of the container and distribution of the liquid processing composition and help in maintaining the layer of processing composition as a structurallystable layer tending to bind the sheets to one another.

As a general rule, the opacifying agent will be present in the layer of liquid spread between the transparent image-receiving sheet and the opaque image-recording sheet in a concentration sufficient to prevent further exposure of the imagerecording medium by actinic radiation transmitted by the transparent image-receiving sheet. Because the silver halide emulsion or emulsions comprising the image-recording strata are thus protected against exposure by incident actinic radiation at one major surface by the opaque processing composition and at the remaining major surface by the opaque support sheet, it is possible to process the film unit subsequent to distribution of the liquid processing composition in the presence of actinic radiation and thereby eliminate the need to provide a processing chamber within the camera and/or make it possible to withdraw the film unit from the camera almost immediately following distribution of the processing liquid. Binding element 20, strip 44 and the material comprising container 16 are also formed of a material opaque to actinic radiation to prevent exposure of the image-recording medium. The opacifying agent is selected for its suitability as a background for viewing the dye-transfer image formed in the dyeable polymeric layer as well as for its opaque property. Another factor considered in the selection of opacifying agent is the requirement that it does not interfere with the formation and color integrity of the dye-transfer image in the image-receiving sheet and that the agent be aesthetically pleasing and does not provide a noisey" background that may degrade the image or detract from the information content thereof. Opacifying agents particularly desirable for incorporation in the liquid processing composition are those providing a white background for viewing the transfer image and particularly those compositions conventionally employed to provide a background for photographic reflection prints and having optical properties particularly suited for the reflection of incident radiation.

As examples of suitable opacifying agents mention may be made of barium sulfate, zinc oxide titanium dioxide, barium stearate, silver flake, silicates, alumina, zirconium oxide. zirconium acetyl acetate, sodium zirconium sulfate, kaolin, mica and the like. An opacifying agent especially preferred because of its high-reflection properties is titanium dioxide and where it is desired to increase the opaqueness of the processing composition containing, for example, titanium dioxide, beyond that ordinarily obtained, an additional opacifying agent such as carbon black may be added in a concentration of about one part carbon black to -500 parts titanium dioxide. A liquid processing composition suitable for incorporation in container 16 for use in combination with sheet materials of type disclosed in the foregoing example is as follows:

1 1.2 grams Water Potassium hydroxide Hydroxyethyl cellulose (high viscosity) [commercially available from Hercules Powder Co. Wilmington, Delaware. under the trade name Nalrasol 250] N-benzyl-a-picolinium bromide Benzotrizole 1.0 gram Titanium dioxide 40.0 grams Reference may be had to the aforementioned copending application for additional details and examples of liquid processing compositions adapted for incorporation of the invention to effect the process thereof.

Subsequent to exposure, film unit 10 is processed as illustrated in FIGS. 2 through 5 of the drawings, by moving the film unit with container 16 foremost relative to and between a pair of juxtaposed members for applying compressive pressure first to the container to eject the fluid contents of the container between the photosensitive and image-receiving sheets 12 and 14 and then spread processing liquid 18 in a uniform, thin layer between the sheets over an area at least coextensive 3.4 grams 1.5 grams with opening 22 in binding element 20 As previously noted.

the processing liquid includes an agent for increasing the viscosity of the liquid so as to promote opening of the discharge passage of the container throughout substantially its entire length and facilitate the discharge of the liquid from the container and spreading of the liquid between the sheets. For this purpose, the liquid should be quite viscous and contain the film-forming material in quantities sufficient to impart a viscosity in excess of 1,000 centipoises at a temperature of C., and preferably of the order of 1,000 to 200,000 centipoises at said temperature.

Preferred means for spreading the processing liquid in a thin layer of uniform predetermined thickness comprise a pair of cylindrical rolls 46 mounted in juxtaposition for rotation about axes located in a common plane and biased toward one another and/or mounted a fixed maximum distance apart so as to apply compressive pressure to the container and elements of the film unit during movement thereof between the rolls. During movement of the film unit between rolls 46, compressive pressure is initially applied to container 16 generating hydraulic pressure in liquid 18 effecting the rupture of the bond between longitudinal marginal sections 38 of the container and the discharge of liquid 18 in the form of an elongated mass between sheets 12 and 14 at end marginal portions 40 and 42 thereof as shown in FIG. 3. Continued movement of the film unit relative to and between spread rolls 46 causes advancement of the mass of liquid between the sheets toward the opposite end thereof and spreading of the liquid as a thin layer 48 of predetermined thickness between and in contact with the facing surfaces of the sheets. A number of expedients are possible for controlling the thickness of the layer of processing liquid distributed between sheets including means in the processing apparatus for appropriately gapping or spacing apart spread rolls 46 and/or components of the film unit capable of performing this function. The film unit illustrated in the drawings is adapted to be employed with cylindrical rolls with the thickness 48 the liquid layer 48 being controlled, as illustrated in FIG. 4, by components of the film unit itself. The spacing between spread rolls 46 and hence the thickness of the layer of processing liquid is determined by the thickness of the film unit at the lateral margins thereof. This thickness is in turn a function of the thickness of the photosensitive and second sheets 12 and 14 and the thickness of lateral edge portions 24 of binding element 20 Since the photosensitive and second sheets are of substantially uniform thickness throughout, the thickness of layer 48 of processing liquid is determined bythe thickness of binding element 29 and is approximately twice the thickness of the binding element. In a typical film unit, for example, the binding element may have a thickness of the order of 0.002 inch and provide for spreading of the processing liquid in a layer having an initial depth of the order of0.004 inch.

To insure spreading of the processing liquid to the edges of the area defined by opening 22 in the binding element and formation of a transfer image extending to the edges of this area, image-receiving sheet 14 is embossed at its lateral edges to displace lateral marginal portions 32 out of the plane of the medial portion of sheet 14 toward sheet 12 by a distance or depth approximating the thickness of binding element 20 or, onehalf of the desired initial thickness of the layer of processing liquid This construction provides for the formation of a layer of processing liquid extending substantially to the lateral edges of opening 22 in the binding element. To further insure the formation of a layer of processing liquid extending at least to the lateral edges of the opening in the binding element, the edge sections of lateral edge portions 24 secured to marginal portions 32 of sheet 14 are wider than the sections of lateral edge portions 24 secured to marginal portions 30 of sheet 12 so that during spreading of the processing liquid between sheets 12 and 14, the inner surfaces of the sheets will be spaced apart in lateral regions extending outside of the edges of opening 22 allowing processing liquid to enter these regions (see FIG, 4) and provide a reservoir of liquid for effecting image-formation within the region of the exposed imagerecording medium immediately adjacent the lateral edges of opening 22. The processing liquid is initially spread as shown in FIG. 4 in a layer having a depth approximately twice the thickness of the binding element and calculated to provide aqueous liquid sufficient to permeate the layer containing the photosensitive medium and efiect formation of a diffusion transfer image. As the liquid permeates the photosensitive layer and is absorbed and/0r dissipated by sheets 12 and 14, the thickness of layer 48 is reduced and the film-forming agent becomes increasingly solid to provide a dimensionally stable opaque layer providing a background for the transfer image and tending to adhere the sheets to one another to preserve the integrity of the film unit structure. The depth of embossing of image-receiving sheet 14 approximates the final thickness of layer 48 to provide an integral laminated assembly of substantially uniform thickness throughout in which layer 48 and the image extend to the edges of opening 22 in binding element 20.

As previously noted, the film unit of the invention is espe- I cially designed'to be processed rapidly, that is, to be moved at a relatively high linear rate (e.g., 9 inches per second) between spread rolls 46 to distribute the processing liquid in a layer that is continuous, is of uniform depth and extends throughout the entire area within opening 22 of binding element 20. These constraints together with the desirability of providing substantially no more than the precise amount of processing liquid required to produce the liquid layer, create substantial problems insofar as spreading of the liquid is concerned. During spreading, liquid 18 is advanced between the sheets as a mass located immediately ahead of spread rolls 46 and extending from side-to-side of the region defined by opening 22. It has been found that air trapped between the sheets during spreading of processing liquid has an adverse effect because it tends to become entrained as air bubbles in the rapidly advancing mass of liquid and the bubbles form voids or discontinuities in the layer of liquid; and additionally, this air between the sheets must be advanced ahead of the mass of liquid and tends to inhibit the advancement of the mass of liquid behind the mass of air. However, if the sheets are initially disposed in face-to-face contact throughout the major portion of the region in which the liquid is to be distributed as a layer and air is excluded from this region between the sheets, not only is air entrainment prevented but spreading of the liquid is facilitated because it is the physical presence of the mass of liquid between the sheets that tends to separate the sheets ahead of the mass of liquid causing the liquid to move forward to fill the otherwise empty space between the separated portions of the sheets. In other words, the mass of liquid tends to separate the sheets immediately ahead of the liquid creating a region of reduced pressure into which the liquid is continuously drawn thereby facilitating the spreading of the liquid at a linear rate greater than would otherwise be possible.

Entrainment of air in the liquid is prevented and enhancement of the spreading rate is achieved by excluding substantially all air from between the sheets particularly in the region thereof immediately ahead of the mass of liquid during spreading of the liquid. This can be accomplished during manufacture of the film unit by assembling the film unit in an environment maintained at a pressure below atmospheric pressure, e.g., in a vacuum, and sealing the sheets together at their margins so as to prevent the admission of air between the sheets. In this embodiment of the film unit binding element 20 and strip 44 are preferably formed of a substantially air impermeable material such as a polymeric film. Alternatively, the film unit may be assembled in an ambient atmosphere and substantially all of the air excluded from between the sheets by pressing the sheets into face-to-face contact throughout substantially the entire area of their facing surfaces before securing the sheets to one another and to the container by binding element 20 and strip 44. In a film unit construction in which the binding element and strip 44 are secured to the sheets in such a way as to substantially prevent the entrance or escape of air, it is important that the quantity of processing liquid be precisely controlled inasmuch as it is virtually impossible for excess liquid to escape from between the sheets at the trailing end thereof. In a film unit construction in which the edge seals provided by the binding element are not completely airtight, particularly at the end of the film unit furthest from the container, which construction may be desirable in some instances to permit escape of relatively small amounts of air from between the sheets during liquid spreading, air may be substantially excluded from between the sheets prior to spreading of the processing liquid by maintaining the film unit, at least in the region of the sheets, under a relatively small compressive force to retain the sheets in face-to-face contact throughout substantially the entire area of their facing surfaces.

It is important to the prevention of air entrainment and the facilitation of spreading that air be excluded from between sheets immediately ahead of the advancing mass of processing liquid and for this purpose the processing apparatus is provided with a second pair of pressure applying members shown in FIGS. 2 and 3 as a pair of juxtaposed rolls 50 located ahead of rolls 46 and spaced therefrom by a distance approximately equal to or slightly greater than the width of the advancing mass of processing liquid so that as the film unit is advanced between rolls 46 to spread the processing liquid, rolls 50 press sheets l2 and 14 into face-to-face contact immediately ahead of the mass of advancing liquid excluding air from between the sheets at least in the region thereof between the rolls. Rolls 50 may perform an additional function of distributing the mass of liquid laterally to insure formation of a liquid layer extending into the corners of opening 22 at the end thereof furthest from container 16. Rolls 50 are spaced from rolls 46 by a distance at least equal to the width of the fluid-filled cavity of container 16 so that rolls 50 do not inhibit the rupture of the container and the discharge of its fluid contents by compressing marginal sections 38 of the container holding the discharge mouth closed while the container is being compressed by rolls 46 to effect discharge of its liquid contents.

in some instances, it may turn out that the quantity of processing liquid provided in container 16 may, during spreading, prove to be slightly in excess of the minimum required to provide the layer between the sheets and necessitate the provision of means for collecting and retaining this excess liquid. Such means are disclosed in U.S. Pat. No. 2,686,? 16 and comprise openings in end marginal portion 36 of sheet 14, overlying end portion 26 of binding element 20 and providing recesses in which any excess liquid is collected and retained.

Another embodiment of a film unit incorporating the invention is illustrated in FIG. 6, wherein the same reference numerals are used to designate components substantially the same as those previously described. This film unit, designated 56, comprises a photosensitive sheet 12 and a second or image-receiving sheet 58 bound to one another by a binding element 20 and differs from film unit primarily in the construction of the fluid-filled container. This container, generally designated 60, is formed by folding an end portion of second sheet 58 transversely upon itself and sealing the folded end portion to itself at the lateral and end edges thereof to form a cavity for containing processing liquid 18. The end edge of second sheet 58 is butted against the end of photosensitive sheet 12 so that the discharge mouth of the container is located at the edge of the sheets. The end section of the second sheet 58 comprising container 60 may be provided on its inner surfaces with a subcoat 62 of a material such as polyethylene, polyvinyl butyryl and the like, which is substantially impermeable to the processing liquid and may be ad hered to itself as by heated sealing. As the case with the container previously described, the longitudinal edge seal of the container extending across the film unit at the end edge of sheet 12 is substantially weaker than the seals at the end of the liquid-filled cavity to provide for the unidirectional release of the liquid between second sheet 58 and photosensitive sheet 12 when the container is subjected to compressive pressure. Sealing strip 44 is secured to the edge of the container and photosensitive sheet 12 to provide a sealed passage between the container and the region between sheets 12 and 58.

Although the film unit of the invention has been described in terms of a component construction incorporating at least two selectively sensitized photosensitive strata in a contiguous relationship and specifically in terms of a tripack structure comprising red-, green-, and blue-sensitive silver halide emulsions having associated therewith, respectively, cyan, magenta, and yellow dye developers, the photosensitive medium of the film unit may comprise at least two sets of selectively sensitized minute photosensitive elements arranged in the form of a mosaic screen with each photosensitive element having associated therewith, for example, an appropriate dye developer in or behind its respective silver halide emulsion portion. in general, such a photosensitive screen will comprise red-sensitized emulsion elements, green-sensitized emulsion elements and blue-sensitized emulsion elements having associated therewith, respectively, a cyan, a magenta and a yellow dye developer.

The film unit of the invention is particularly adapted to the production of color images by a variety of additive processes and/or for the production of other visual effects including stereoscopic pictures and cinematography. Additive color images may be produced by employing a suitable screen in place of the transparent image-receiving sheet and for additive color photographs, this screen may comprise a mosaic of minute color filter elements, for example, of the primary colors, red, green and blue, or a lenticular screen. Processes of this type are well known in the art for producing monochrome images (e.g., black and white), which, with the aid of appropriate screens, can be exhibited in full color and/or to produce other visual effects including stereoscopic and cinematographic.

In the preceding description, photographic film units and processes have been described adapted to the production of positive prints either in black and white or color adapted to be viewed or exhibited by reflected light. The film units and the processes of the invention are also adapted to the production of visible images designed to be exhibited by light transmitted through the film unit; and in such an embodiment, all of the layers of the film unit would be formed of transparent materials and the visible image may be either a positive or negative image. In the case of a positive transfer image together with a negative image, the higher covering power of the positive image (silver will enable the positive image to be viewed by transmitted light without any noticeable adverse effect due to the presence of the negative image.

There will be seen from the foregoing that the film unit described as embodying the invention and the process employing the film unit'are made possible by the film unit construction represented by a more convenient, simplified and less expensive photographic system by which it is possible to produce high quality and aesthetically pleasing photographic prints employing novel and improved photographic apparatus. The film unit is self-contained and is readily and easily stored, handled and processed; and the method of the invention provides for the rapid processing of the film unit while insuring the production of high-quality results.

Since certain changes may be made in the above product and process without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. in a photographic film unit comprising a photographic image-recording sheet including a photosensitive material capable of recording an image when exposed to actinic light, a second sheet, at least one of said sheets being transparent to actinic light, and a collapsible container carrying a quantity of a viscous processing liquid sufficient to form a layer of predetermined uniform thickness over facing areas of said sheets and including an agent capable, when spread in a layer of predetermined thickness between and in contact with said sheets, of reacting with said photosensitive material following the exposure thereof to produce an image between said sheets visible through one of said sheets, said container having sections defining a discharge passage through which the liquid contents of said container can be ejected by the application of compressive pressure thereto, the improvement comprising:

binding means secured to the outer surfaces of said sheets at the margins thereof along three sides of said sheets for securing said sheets in face-to-face relation preventing admission of air between said sheets at least at the lateral margins thereof and preventing escape of processing liquid from between said sheets, said sheets being held together by said binding means in contacting relation over substantially their entire facing surfaces to define a region bound by said facing surfaces that is substantially free of air;

said binding means including means securing said container to said sheets along a fourth side of at least one of said sheets and forming a substantially liquidtight seal between said section of said container and said sheets at an edge of said air-free region.

2. A photographic film unit as defined in claim 1 wherein the said binding means provide a seal completely around the periphery of said air-free region in which said liquid is spread for preventing admission of air between said sheets into said region.

3. The method of rapidly spreading a viscous photographic processing liquid in a continuous, uniform layer between a pair of superposed photographic sheets without entraining air in said liquid, said method comprising:

superposing said sheets in face-to-face contact throughout substantially the entire area of their facing surfaces so as to exclude substantially all air from a region between said sheets extending to the edges of at least one of said sheets;

progressively applying compressive pressure to a collapsible container of said liquid attached to the exterior of said sheets at one edge thereof to generate hydraulic pressure within said liquid in said container to force said liquid into said region between said superposed sheets at said one edge thereof;

continuing the progressive application of compressive pressure to said sheets for advancing said liquid as a mass toward said opposite edge of said sheets to separate said sheets in a region thereof immediately ahead of said mass of said liquid and spread said liquid in a layer between said sheets; and

during advancement and spreading of said liquid, sealing said sheets together at their lateral marginal edges extending in the direction of advancement and spreading of said liquid, to prevent admission of air between said sheets and escape of said liquid from between said sheets at said lateral marginal edges, and maintaining transverse portions of said sheets immediately ahead of said mass of liquid in face-to-face contact to prevent entrainment of air in said mass of liquid being advanced between said sheets.

4. A method of rapidly spreading a viscous photographic processing liquid between a pair of superposed sheets as defined in claim 3 wherein compressive pressure is applied to a transverse portion of said superposed sheets immediately ahead of said mass of liquid being advanced between said sheets to retain said transverse portion of said sheets in faceto-face contact and prevent admission of air therebetween. 

2. A photographic film unit as defined in claim 1 wherein the said binding means provide a seal completely around the periphery of said air-free region in which said liquid is spread for preventing admission of air between said sheets into said region.
 3. The method of rapidly spreading a viscous photographic processing liquid in a continuous, uniform layer between a pair of superposed photographic sheets without entraining air in said liquid, said method comprising: superposing said sheets in face-to-face contact throughout substantially the entire area of their facing surfaces so as to exclude substantially all air from a region between said sheets extending to the edges of at least one of said sheets; progressively applying compressive pressure to a collapsible container of said liquid attached to the exterior of said sheets at one edge thereof to generate hydraulic pressure within said liquid in said container to force said liquid into said region between said superposed sheets at said one edge thereof; continuing the progressive application of compressive pressure to said sheets for advancing said liquid as a mass toward said opposite edge of said sheets to separate said sheets in a region thereof immediately ahead of said mass of said liquid and spread said liquid in a layer between said sheets; and during advancement and spreading of said liquid, sealing said sheets together at their lateral marginal edges extending in the direction of advancement and spreading of said liquid, to prevent admission of air between said sheets and escape of said liquid from between said sheets at said lateral marginal edges, and maintaining transverse portions of said sheets immediately ahead of said mass of liquid in face-to-face contact to prevent entrainment of air in said mass of liquid being advanced between said sheets.
 4. A method of rapidly spreading a viscous photographic processing liquid between a pair of superposed sheets as defined in claim 3 wherein compressive pressure is applied to a transverse portion of said superposed sheets immedIately ahead of said mass of liquid being advanced between said sheets to retain said transverse portion of said sheets in face-to-face contact and prevent admission of air therebetween. 